Railway retarder control system

ABSTRACT

A control system for a railway car retarder comprising an elongated notched sensing rail engaged by an overhanging part of a car wheel (the wheel flange or the outer edge of the wheel tread), with a control that determines car speed in accordance with vibration of the sensing rail. Resilient mounting is used for the sensing rail, to minimize wear and provide vibration isolation, with dampening to avoid mechanical resonance at frequencies in the operating speed range. A separate car presence detector, actuated by the sensing rail, is included.

United States Patent Inventors Rosser 1... Wilson Mahwah, N..1.; Robert W. Convey, Oakland, N.J.; Earl E. Frank, Tallman, N.Y. Appl. No. 853,129 Filed Aug. 26, 1969 Patented Sept. 28, 1971 Assignee Abex Corporation New York, NY.

RAILWAY RETARDER CONTROLSYSTEM Primary ExaminerArthur L. La Point Assistant ExaminerGeorge H. Libman Attorney-Kinzer, Dam and Zickert ABSTRACT: A control system for a railway car retarder comprising an elongated notched sensing rail engaged by an overhanging part of a car wheel (the wheel flange or the outer edge of the wheel tread), with a control that determines car speed 9 Claims 5 Drawing in accordance with vibration of the sensing rail. Resilient 11.8. C1 246/182 A, mounting is used for the sensing rail, to minimize wear and 104/26 A, 246/ 1 69 R provide vibration isolation, with dampening to avoid mechani- Int. Cl. B611 l/04 cal resonance at frequencies in the operating speed range. A Field 01 Search 246/169 R, separate car presence detector, actuated by the sensing rail, is

246, 251, 182 A; 104/26 A included.

|5 Run-Arman 3 Acrurnoa l r ,1 A 145 41-- f H 2 SIGNAL 1 I 22 23 f 4 S compassion! cu PPER A zlxflgzgl e j AMPLIFIER F In 21 28 26 i l "t f LOW-PASS DRVER FH'TER SIGNAL CRELAY 2 25 AND QNTROL l i man-Pass F'LTER NOISE BRAKE l C NTROL RELAY Punsenct CONTROL PATENTEDSEP28|97l 3,609,350

SHEET 2 [IF 3 ii I! I45 H p m t m ax w Invenl'orS ROSsERL-WIL ROBERT W.Co:-|vEY EARL E. FRANK PATENTEUSEP28|9H I 3,609,350

in M IIIII Jum U lhw Inventors ROSSER L. WILSON ROBERT W.Cor-w&-r

EARL E. FRANK RAILWAY RETARDER CONTROL SYSTEM BACKGROUND OF THE INVENTION In the control of a railway car retarder, particularly in a classification yard, it is often necessary to have an accurate and effective continuing determination of the speed of individual railway cars or cuts of cars as they move through the retarder. Accurate speed sensing makes it possible to release each cut at an appropriate speed so that it will reach its desired destination in the classification yard without damage to the car or its contents.

An effective speed-actuated retarder control system is described in U.S. Pat. No. 3,240,930 to Richard E. Porter and Arthur R. Crawford, issued Mar. 15, 1966. In the control system described in that patent, a rail extending through a major portion of the retarder is provided with a series of notches or other surface discontinuities that are equally spacedalong the rail in position to be engaged by the wheel of a railway vehicle moving along the rail. Speed detection is effected by one or more vibration transducers, mounted on the rail, the frequency of vibration of the rail is determined by the spacing of the notches and the rate at which the wheel engages the notches. This basic system has proved effective and accurate in a variety of individual applications.

In systems in which the notched rail is a traffic rail, as in the particular apparatus illustrated in the Porter et al. patent, operating difficulties may be encountered in some installations; for example, a mechanical resonance condition may cause the traffic rail to continue vibrating at a given rate even though the retarder has slowed the car below the speed that would normally produce that particular vibration rate. A badly deformed railway wheel may cause a heavy pounding of the rail that overrides the vibrations caused by the wheel engagement with the rail notches, creating a confused or erroneous operation on the part of the speed-sensing control. At times, the closing of switches in adjacent track sections may cause rail vibrations that can result in errors in operation of the retarder control. In addition, in some systems in which the presence of a car in the retarder is detected solely on the basis of the traffic rail vibration, a loss of control may occur if a car stops within the retarder control zone.

SUMMARY OF THE INVENTION It is a principal object of the invention, therefore, to provide a new and improved speed-sensitive control system for a railway car retarder that effectively and inherently overcomes the difficulties of previously known vibration-actuated systems as described above.

A more specific object of the invention is to provide a new and improved speed control system for a railway car retarder that utilizes a separate sensing member or rail that is engaged by the wheel of a car traversing the retarder but is isolated from the traffic rails to avoid errors in operation that might otherwise be caused by extraneous vibration of the traffic rail due to the presence of wheel deformations or to other external factors.

Another object of the invention is to provide a new and improved speed-sensitive control system for a railway car retarder that affords a convenient and inexpensive means for accurate determination of the presence of a car in the retarder independently of the speed determination.

A further object of the invention is to provide a new and improved speed sensitive control system for a railway car retarder, based upon vibration of an auxiliary sensing rail engaged by an overhanging portion of a railway car wheel, that avoids undesirable mechanical resonance in the system and that minimizes wear on the speed-sensing elements of the system.

Accordingly, the invention is directed to a speed-sensitive control system for a railway car retarder employed to brake a railway car as the car traverses a given segment of a traffic rail. The system comprises an elongated sensing member mounted adjacent the aforesaid traffic rail segment, this sensing member having a sensing surface positioned for engagement by an overhanging portion of a railway car wheel as the wheel rolls along the traffic rail. The sensing surface of the sensing member has a series of discontinuities, usually notches, at predetermined equally spaced intervals, these intervals being substantially smaller than the circumference of a car wheel. Vibration isolating means is provided to isolate the sensing member from vibration of the traffic rail. Transducer means are mounted on the sensing member to generate an initial electrical signal representative of vibration of the sensing member caused by contact with a railway wheel moving therealong, that signal including repetitive signal components at frequencies determined conjointly by the spacing between the aforesaid surface discontinuities and by the speed of movement of the wheel. Control means are coupled to the transducer means to develop, from the initial electrical signal, a control signal representative of the speed of the railway car wheel relative to a given standard. The system further includes means for actuating the retarder between braking and release conditions in response to the control signal.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a block diagram of a railway car retarder incorporating a control system that utilizes speed sensing apparatus constructed in accordance with one embodiment of the present invention;

FIG. 2 is a detail side elevation view of a part of the speed sensing apparatus of FIG. 1;

FIG. 3 is a sectional elevation view taken approximately along line 3-3 in FIG. 2;

FIG. 4 is a detail elevation view, similar to FIG. 2, of another embodiment of the present invention; and

FIG. 5 is a sectional elevation view taken approximately along line 55 in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates the application of one embodiment of the present invention to the control of a railway car retarder 10. Car retarder 10 includes a segment of a traffic rail 11 along which a railway car may roll in the direction indicated by the arrow A. A pair of car-retarding rails or brake shoes 12 and 13 are disposed immediately adjacent rail II in position to engage the opposite sides of a car wheel as it traverses this portion of the traffic rail, only a small section of retarder rail 12 is shown in FIG. 1, most of this rail being cut away to permit illustration of operating elements of the control system of the invention. Of course, retarder l0 may include a second pair of retarder rails along the other rail of the railway (not illustrated).

An actuating mechanism 15 is provided for actuating retarder rails (e.g. rails 12 and 13) of retarder l0. Retarder actuating mechanism 15 may be any suitable electrical, mechanical, pneumatic or hydraulic mechanism capable of moving retarder rails 12, and 13 between an open released position and a closed braking position. When the retarder rails are in the released position, a car rolling along traffic rail segment 11 passes through retarder 10 without substantial braking. When the retarder rails are in their braking position, however, the rails engage the sides of the car wheels and provide a substantial braking effect on the rolling car.

An elongated sensing member 14 is mounted adjacent traffic rail segment 11. Sensing member 14 has an upper sensing surface that is provided with a series of surface discontinuities 16 at equally spaced intervals along the length of the sensing member. These surface discontinuities 16 comprise a series of shallow grooves in sensing surface 143, the grooves extending transversely of that surface. By way of example, the grooves 16 in sensing surface 148 may be of the order of oneeighth to one-half inch wide; the grooves may be relatively deep because sensing member 14 carries little or no load. The spacing S between the discontinuities 16 is not particularly critical, except that this spacing should be made substantially smaller than the circumference of a railway wheel and should also be substantially smaller than the spacing between any two adjacent wheels on a railway truck. Typically, the spacing S between grooves 16 may be of the order of one to five inches. Whatever the selected spacing for the discontinuities 16, the spacing should be maintained constant to afford an effective means for causing sensing member 14 to vibrate at frequencies representative of the speed of a car moving into and through retarder 10.

It is not essential that the discontinuities 16 take the form of shallow grooves. Instead, small projections may be formed on the sensing surface 148, since the purpose of the discontinuities is to set up a vibration in sensing member 14 that is proportional to the speed of a railway car wheel moving along rail 11. The grooved construction described hereinabove is preferred, however, because it affords the least problems with respect to machining and maintenance.

The system of FIG. 1 also includes transducer means for generating an initial electrical signal that is representative of vibration of sensing member 14. This transducer means comprises three individual transducer 17A, 17B and 17C that are mounted on sensing member 14. A variety of different specific fonns of vibration-sensitive transducer may be utilized for the devices 17A-17C. Typically, these devices may comprise conventional velocity-actuated transducers each capable of producing an electrical output signal directly representative of vibration of the member upon which they are mounted, sensing member 14. Inasmuch as pickup devices of this kind are well-known in the art and are commercially available, construction of the pickups is not described in detail herein.

Sensing member 14 preferably extends ahead of the retarder rails 12 and 13. This relationship is not critical, however, and is shown only to afford a complete illustration of this embodiment of the invention.

Transducers 17A-17C are electrically connected to a speed control unit 18. Control unit 18 may include frequency-sensitive means for segregating, from the initial electrical signals developed by transducers 17A-17C, speed-representative signals comprising repetitive components of the initial electrical signal produced by engagement of a car wheel with the surface discontinuities 16 in sensing member 14. That is, speed control unit 18 provides for the effective elimination of extraneous vibrations, in the signals from the transducers 17A-17C, such as might be produced by an irregularity in a car wheel, or by some other source of extraneous vibration. Speed control unit 18 also includes means for utilizing the speed-representative signals to develop a control signal, suitable for controlling operation of the retarder actuating mechanism 15.

In control unit 18 the transducers 17A-17C are connected to an automatic signal level selector circuit 21. Circuit 21 is employed to select the signal of maximum amplitude, from the transducers, so that a single signal may be utilized to actuate the remaining circuits of control unit 18. It is not essential that three pickup devices be employed; instead, a single pickup or two transducers may be utilized. On the other hand, additional pickups may be included in the system if desired. In a given application, the optimum number of transducers is dependent primarily upon the sensitivity of the transducers utilized and the damping characteristics of sensing member 14 and its mounting.

The output of signal selector 21 is coupled to a compressor amplifier 22 that functions primarily as an automatic gain control for the system. The compressor amplifier may include, in its output stage, a high-pass filter with a relatively low cutoff frequency, this filter being employed to eliminate, to a substantial extent, the effect of extraneous very-low-frequency signals. The compressor amplifier is coupled, in turn, to a clipper circuit 23 that is connected to an adjustable low-pass filter 24. Adjustable filter 24 is the speed selection device of the system and is employed to adjust the system to release cars .from retarder at varying speeds dependent upon the requirements of the classification yard in which the retarder is used. It is essential that filter 24 have a sharp cutoff characteristic in order to afford adequate differentiation between different desired output speeds.

The output of filter 24 is coupled to a driver amplifier 25 utilized to actuate a signal relay and control circuit 26. Circuit 26, in turn, actuates a brake relay circuit 27 that is electrically connected to retarder actuating mechanism 15 to control the operation of retarder 10.

In addition to the connection to clipper circuit 23, the output of compressor amplifier 22 is coupled to a low-pass filter 28 that is connected in series with a high pass filter 29 to a noise control circuit 31. Noise control circuit 31 is coupled to signal relay circuit 26. A portion of the signal relay of circuit 26 is incorporated in a bypass circuit that shunts low-pass filter 28 for certain operating conditions, as described more fully hereinafter.

Control unit 18 further includes presence detector means comprising a pair of presence detector devices 61A and 61B. Devices 61A and 618 may constitute simple mechanically actuated limit switches located below sensing member 14 in position to detect downward movement of the sensing member when a car passes through the retarder. Detectors 61A and 61B are electrically connected to a presence control circuit 62 that is in turn connected to the signal relay and control circuit 26.

In considering operation of the system illustrated in FIG. 1, it may first be assumed that there is no car entering retarder 10. REtarder actuating mechanism 15 is set to maintain the retarder open. Since no car is rolling over traffic rail segment 11, there are no output signals from transducers 17A-17C, except possible low-amplitude noise signals of short duration. These signals are not effective to actuate control system 18, so that the retarder remains in its open or released braking condition, Moreover, the presence detectors 61A and 61B are not actuated.

A car wheel entering retarder l0 first engages the notched sensing surface 148 of sensing member 14 at point 14A, the direction of car entrance being indicated by arrow A. Movement of the car wheel along sensing member 14 produces a vibration in the sensing member having frequency components determined by the spacing of notches 16 and by the speed at which the car is moving, with some harmonics. Vibration of sensing member 14 is sensed by transducers 17A-17C, producing initial electrical signals having repetitive components at frequencies corresponding to the frequencies at which the sensing member is vibrated. When the car first engages sensing member 14, at point 14A, the signal produced by the first transducer 17A is substantially stronger than that produced by the second pickup 178, since the car is closer to transducer 17A and, accordingly, the damping effect of transmission of vibration along member 14 is less with respect to the first pickup unit.

The output signal from transducer 17A, accordingly is selected by circuit 21 and supplied to compressor amplifier 22. The compressor amplifier and clipper 23 serve primarily to maintain a constant amplitude output despite substantial variations in the amplitude of the signal received from the transducer. This automatic gain control effect is desirable because the amplitude of the output signal from the transducer may vary to a substantial extent as the car moves along traffic rail segment 11.

Filter 24 is set, in advance, to a given frequency determined by the desired maximum speed for cars leaving the retarder. Assuming that the car enters at a speed above the preset exit speed, the signal from clipper 23 is composed primarily of frequencies higher than the setting of filter 24. Consequently, the signal is substantially attenuated and does not effect operation of the signal relay and control circuit 26. The same signal, however, is supplied to noise amplifier 31 through filter circuit 28 and 29. The signal supplied to noise amplifier 31 actuates a noise relay, in circuit 31, completing an energizing circuit for the signal relay of unit 26. Upon actuation of the signal relay, brake relay 27 is energized to complete an operating circuit that supplies a control signal to retarder actuating mechanism 15. ln addition, the car wheel depresses sensing member 14 to some extent, as explained more fully hereinafter, completing an electrical circuit that actuates presence control62 and signal the presence of a car to circuit 26. Accordingly, mechanism 15 is energized to actuate retarder to closed condition.

Closing of the retarder is preferably accomplished before the railroad car reaches retarder rails 12, 13. it is for this reason that the serrated sensing member 14 is extended well ahead of the retarder mechanism, giving sufficient time to close the retarder before the car reaches braking position.

When the car is engaged by retarder rails 12 and 13, it is decelerated at a rate depending upon the weight of the car, its initial speed, the braking force applied to the retarder rails by the retarder actuating mechanism, and other factors common to rail retarder systems. When the car is decelerated to a speed below the exit velocity for which filter 24 is adjusted, the filter applies a signal to driver amplifier 25 which in turn actuates circuit 26 to deenergize the signal relay. When the signal relay drops out, the operating circuit for brake relay 27 is interrupted, with the result that the control signal applied to mechanism is changed and mechanism 15 actuates retarder 10 to its released position.

When signal relay 26 drops out, at the time that braking of the car is completed, the bypass circuit for low-pass filter 28 in the noise channel of the system is opened, effectively placing the low-pass filter in the signal channel to the noise amplifier 31. This is done to prevent high order harmonic signals from holding the noise relay energized at speeds below a predetermined minimum setting established as the lower limit of retarder control. In a typical system, this minimum setting may be of the order of three miles per hour, with retarder control afforded over a range of 3 to 15 miles per hour as determined by the setting of adjustable filter 24.

. As noted above, retarder 10 is opened or released while the car is still moving. Consequently, under ordinary circumstances the car continues its movement through the retarder, at its reduced speed, and eventually passes beyond the exit end 14B of sensing member 14. When this occurs, the signal supplied to the control system 18 is no longer adequate to energize the noise relay in circuit 31, with the result that the noise relay drops out and the system is ready for a subsequent operation. The noise relay also drops out if the car speed drops below the minimum range of retarder operation, as noted above, due to the operation of high-pass filter 29.

When a car first enters the retarder control system, at point 14A, the predominant signal is that supplied by transducer 17A. MOvement of the car through the retarder, however, eventually results in production of a signal at transducer 178 that is of greater amplitude than the signal from the initial pickup 17A. When this happens, selector 21 transfers control of the system from the initial transducer 17A to the second transducer 178. Subsequently, as the car nears the end of the retarder, control is switched to transducer 17C.

Control unit 18, as illustrated in FIG. 1 and described above, is essentially similar to the retarder control system illustrated in FIG. 1 of the aforementioned US. Pat. No. 3,240,930 to Porter et al., but with one substantial modification. In the control system described in the patent, the presence of a car in the control zone for the retarder is detected by noise control 31. This function may be compromised if there is an undesired drop out of the relay or other presence detection components of the noise control circuit, as may occur when the signal supplied to the noise control is abnormally low in amplitude, when the car stops and the vibration signal is consequently interrupted, or under other circumstances. In the control system of the present invention, this difficulty is eliminated by the additional presence control comprising the presence detector 61A and 61B and the presence control 62, which are utilized to maintain the system in operation even if the car stops entirely in the retarder control zone. lt should be understood that control unit 18 may be replaced by any of the other control systems disclosed in the Porter et al. patent or by other equivalent electrical circuits for utilizing the initial signals developed by transducers 17A and 17C, together with the presence signals from detectors 61A and 618. Other types of presence detectors could be employed.

A principal feature of the present invention is the provision of the separate sensing member 14 as an integral part of the portion of the control system that develops the original vibration-induced signals representative of the speed of a railway car wheel traversing traffic rail 11. A typical construction employed for sensing member 14, and its mounting on rail 11, are best illustrated in FIGS. 2 and 3. As shown therein, the elongated sensing member 14 has a base flange 41 supporting an upwardly projecting web 42 which terminates in a head portion 43, the upper surface of the head portion 43 constituting the sensing surface 14S with its notches 16. The base flange 41 of sensing member 14 is supported upon a series of coil springs 44 that are in turn mounted upon a plate 45. Plate 45 is secured to the base 46 of traffic rail 11 by appropriate means such as a series of bolts 47. Thus, sensing member 14 is permitted limited vertical movement by virtue of the spring mounting afforded by springs 44.

The transducers 17A-17C for the control system of the invention are directly mounted upon the web portion 42 of sensing member 14, as shown by transducer 17A in FIGS. 2 and 3. The end portion 14A of sensing member 14 is sloped, as shown in FIG. 2, to provide a gradual engagement with a railway car wheel such as the wheel 48. As shown in H6. 2, the presence detector device 61A is mounted on the base 46 of rail 11 and has an upwardly projecting sensing element 64 that engages the bottom of sensing member 14. A similar mounting is employed for detector 613 (not shown in FIG. 2). In addition, a plurality of motion dampeners 63 may be mounted along rail 11, between base 46 and sensing member 14, to prevent development of an undesirable mechanical resonance in the mounting for the sensing member.Dampeners 63 may be friction devices, or pneumatic or hydraulic pistons.

In operation, the wheel 48 moving along traffic rail 11 first engages the sloped initial portion 14A of sensing member 14. The flange 49 of the wheel, overhanging the head of the traffic rail, engages the upper surface 14S of the sensing member. Variations in the diameter of the flanges 49 on different railway wheels are effectively compensated by the spring mounting for sensing member 14. As the wheel continues its movement along traffic rail 11, it passes over each of the notches 16 in sensing member surface 145, producing characteristic vibrations representative of the speed at which the wheel is moving along the rail. lt is these vibrations that are picked up by the transducers, such as transducer 17A, to afford the initial electrical signals necessary to operation of control unit 18 (FIG. 1). Downward deflection of sensing rail 14 is detected by device 61A.

If the tread 51 of wheel 48 has a substantial flat spot, it creates a heavy pounding vibration in rail 11. This extraneous vibration tends to produce misleading and inaccurate results in the output signals from the transducers of the system. In the construction shown in F168. 2 and 3, however, the springs 44 afford an effective vibration isolating means that materially reduces the amplitude of vibrations induced in sensing member 14 as the result of flat spots or other irregularities in the wheel tread. Moreover, vibrations of the traffic rail 11 that may be created by opening and closing of switches near the re tarder, or from other sources, are substantially-reduced in amplitude, as applied to sensing member 14, due to the vibration isolation afforded by the spring mounting for the sensing member.

The use of a separate sensing member, independent of the traffic rail, as the main input to the control system of the invention, affords other substantial advantages. Sensing member 14 can be constructed to afford a natural resonant frequency that is well outside of the range of operating frequencies for the speed vibration signals picked up by transducers 17A-17C. Dampeners 63 can be readily selected to aid the overall system objectives, in this regard. This is not readily possible where a traffic rail is used as a sensing member, due to the structural requirements of the traffic rail itself. Moreover, the rim of the wheel flange 49 of a railway wheel remains substantially unchanged throughout the life of the wheel, even though the tread may develop flat spots and may require machining. Stated differently, there is little or no tendency toward the development of irregularities in flange 49, with the result that the extraneous vibrations produced by wheel deformations are not reproduced in the control system of the present invention.

The service life of sensing member 14 can be virtually indefinite in duration. Sensing member 14 does not carry any substantial part of the weight of the railway cars passing through the retarder. The contact of the sensing member with the wheel flange is controlled by the compliance of the springs 44 (and by the give of dampeners 63, when used), which may be made soft" enough so that the wear on notches 16 and on the intervening portions of surface 145 is minimal. Presence detection may be made independent of speed detection, by use of detectors 61A, 61B. The combination of these attributes, afforded by the use of the separate sensing member 14, provides substantially greater reliability and effectiveness in the operation of control unit 18.

Another structural embodiment of the present invention, entailing a different configuration and mounting arrangement for the sensing member, is illustrated in FIGS. 4 and 5. In the construction shown in those FIGS., the elongated sensing member 114 is mounted on the field side of rail 11 and is formed of relatively heavy gauge sheet steel or plate. The upper portion of sensing member 114 comprises a sensing surface 1148 in which a plurality of individual notches or other surface discontinuities 16 are formed at equally spaced intervals. The entrance end of sensing member 114 is sloped as indicated at 114A to provide a smooth transitional engagement with the overhanging portion of the tread 51 of a wheel 48 as the railway wheel moves into the control zone for the car retarder. A similar slope (not shown) is provided at the opposite end of sensing member 114 to afford a smooth transition as the railway wheel leaves the retarder.

The lower portion of sensing member 114 is bent inwardly to afford a mounting section 115 that extends parallel to and in engagement with the web of traffic rail 11. At the bottom of section 115, sensing member 114 is bent outwardly to afford a support flange 116. Flange 116 is mounted upon a resilient pad 144 that may be formed of synthetic rubber or other elastomeric material.

A series of mounting guides 119 are utilized to mount the sensing member 114 on traffic rail 11. As best shown in FIG. 5, each of the mounting guides 119 comprises a shaft that extends from the mounting portion 115 of sensing member 114 through an aperture 121 in the web of rail 11 and out the opposite side of the rail web. The projecting end of the mounting guide 119 carries a spring 122 that maintains mounting member 114 in aligned position relative to the traffic rail but that allows some limited movement of sensing member 114 relative to the traffic rail. It should be noted that the aperture 121 in the web of the rail is elongated in a vertical direction to permit limited vertical movement of sensing member 114 with respect to rail 11.

The operational characteristics of the construction illustrated in FIGS. 4 and are generally similar to those of the previously described construction of FIGS. 2 and 3. As the railway car wheel 48 enters the retarder control zone in the direction of arrow A, it rolls smoothly up the sloped entrance portion 114A of sensing member 114. Actually, the sensing member does not carry the weight of the wheel, but is depressed slightly by the wheel, which then moves across sensing surface 1148 in continuing engagement therewith. The continuing engagement of the wheel tread 51 with sensing surface 1145 causes sensing member 114 to vibrate at a rate determined conjointly by the speed of the car wheel 48 and by the spacing between the surface discontinuities 16 of sensing surface 1148.

In the construction shown in FIGS. 4 and 5, the resilient pad 144 supporting sensing member 114, and the springs 122 utilized in the support and guide members 119, provide an effective vibration isolation means that materially reduces the amplitude of vibrations induced in sensing member 114 as a result of extraneous vibration of traffic rail 11. The springloaded mounting guides 119 can be constructed to prevent development of a resonance condition within the range of operation frequencies for the speed vibration signals picked up by the transducers such as transducer 17A. Effective dampening for the sensing member 114 is achieved by judicious selection of the springs 122 and the resilient support pad 144. If necessary, auxiliary dampeners, such as the device 63 illustrated in FIG. 2, could be incorporated in the construction of FIGS. 4 and 5, but separate dampeners are not usually necessary, due to the inherent dampening effect caused by frictional engagement between the web of traffic rail 11 and the mounting portion of sensing member 114. Of course, it will be recognized that separate position detectors such as the position detector 61A (FIGS. 1 and 2) can be readily incorporated in the construction shown in FIGS. 4 and 5.

We claim: 1. A speed-sensitive control system for a railway car retarded employed to brake a railway car or like vehicle as the car traverses a given segment of a traffic rail, comprising:

an elongated sensing member mounted adjacent said segment of the traffic rail and having a sensing surface positioned for engagement by an overhanging portion of a railway car wheel as the wheel rolls along the traffic rail,

said sensing member having a series of surface discontinuities at predetermined equally spaced intervals, along said sensing surface, the spacing between adjacent discontinuities being substantially smaller than the circumference of a railway car wheel;

vibration isolating means, isolating said sensing member from said rail, said vibration isolating means comprising a resilient support mounted on the base of said traffic rail segment, said sensing member being mounted on said resilient support;

dampener means, between said traffic rail and said sensing member, for damping movements of said sensing member to preclude mechanical resonance thereof in the operating range of vibrational frequencies for said sensing member;

transducer means, mounted on said sensing member, for

generating an initial electrical signal representative of vibration of the sensing member caused by contact with a railway wheel moving therealong and including repetitive signal components at frequencies determined conjointly by the spacing between said surface discontinuities and the speed of movement of the wheel;

control means, coupled to said transducer means, for

developing, from said initial electrical signal, a control signal representative of the speed of the railway car wheel relative to a given standard;

and means, coupled to said control means for actuating said retarder between braking and release conditions in response to said control signal.

2. A railway car retarder control system according to claim 1 in which said sensing member is mounted on the gauge side of the traffic rail in position for said sensing surface to be engaged by the rim of the flange on said railway wheel.

3. A railway car retarder control system according to claim 1 in which said sensing member is mounted on the field side of the traffic rail in position for said sensing surface to be engaged by the outer edge portion of the tread of said railway wheel.

4. A railway ear retarder control system according to claim 1, in which said resilient support comprises a plurality of individual compression springs mounted on the base of said traffic rail segment at spaced intervals therealong.

5. A railway car retarder control system according to claim 1, in which said resilient support comprises an elongated block of elastomer material.

6. A railway car retarder control system according to claim 1, and further including a plurality of guide members, interconnecting said sensing member and said traffic rail, for maintaining said sensing member in alignment with said traffic rail despite limited vertical movement of said sensing member.

7. A railway car retarder control system according to claim I, in which said dampener means comprises a plurality of fluid pistons interposed between said traffic rail base and said sensing member.

8. A railway car retarder control system according to claim 1, and further comprising car presence detector means for detecting the presence of a railway car on said traffic rail segment in accordance with downward displacement of said sensing member, independently of continuing movement of the car.

9. A railway car retarder control system according to claim 1, in which said sensing member moves through a limited distance each time it is engaged by a car wheel, and further comprising car presence detector means for detecting such movement of said sensing member to determine when a car is present independently of continuing movement of the car. 

1. A speed-sensitive control system for a railway car retarder employed to brake a railway car or like vehicle as the car traverses a given segment of a traffic rail, comprising: an elongated sensing member mounted adjacent said segment of the traffic rail and having a sensing surface positioned for engagement by an overhanging portion of a railway car wheel as the wheel rolls along the traffic rail, said sensing member having a series of surface discontinuities at predetermined equally spaced intervals, along said sensing surface, the spacing between adjacent discontinuities being substantially smaller than the circumference of a railway car wheel; vibration isolating means, isolating said sensing member from said rail, said vibration isolating means comprising a resilient support mounted on the base of said traffic rail segment, said sensing member being mounted on said resilient support; dampener means, between said traffic rail and said sensing member, for damping movements of said sensing member to preclude mechanical resonance thereof in the operating range of vibrational frequencies for said sensing member; transducer means, mounted on said sensing member, for generating an initial electrical signal representative of vibration of the sensing member caused by contact with a railway wheel moving therealong and including repetitive signal components at frequencies determined conjointly by the spacing between said surface discontinuities and the speed of movement of the wheel; control means, coupled to said transducer means, for developing, from said initial electrical signal, a control signal representative of the speed of the railway car wheel relative to a given standard; and means, coupled to said control means for actuating said retarder between braking and release conditions in response to said control signal.
 2. A railway car retarder control system according to claim 1 in which said sensing member is mounted on the gauge side of the traffic rail in position for said sensing surface to be engaged by the rim of the flange on said railway wheel.
 3. A railway car retarder control system according to claim 1 in which said sensing member is mounted on the field side of the traffic rail in position for said sensing surface to be engaged by the outer edge portion of the tread of said railway wheel.
 4. A railway car retarder control system according to claim 1, in which said resilient support comprises a plurality of individual compression springs mounted on the base of said traffic rail segment at spaced intervals therealong.
 5. A railway car retarder control system according to claim 1, in which said resilient support comprises an elongated block of elastomer material.
 6. A railway car retarder control system according to claim 1, and further including a plurality of guide members, interconnecting said sensing member and said traffic rail, for maintaining said sensing member in alignment with said traffic rail despite limited vertical movement of said sensing member.
 7. A railway car retarder control system according to claim 1, in which said dampener means comprises a plurality of fluid pistons interposed between said traffic rail base and said sensing member.
 8. A railway car retarder control system according to claim 1, and further comprising car presence detector means for detecting the presence of a railway car on said traffic rail segment in accordance with downward displacement of said sensing member, independently of continuing movement of the car.
 9. A railway car retarder control system according to claim 1, in which said sensing member moves through a limited distance each time it is engaged by a car wheel, and further comprising car presence detector means for detecting such movement of said sensing member to determine when a car is present independently of continuing movement of the car. 